A fire burning in the dried-up bed of Lake Okeechobee is the most likely source of that smoky smell pestering residents in southern and western Palm Beach County.

The Division of Forestry, the Boca Raton Fire Department dispatchers, Palm Beach County Fire Rescue all report several calls from residents in the Boca Raton area complaining of smoke. But earlier in the morning, its source was elusive.

The Palm Beach County Health Department issued a warning that air quality reached unhealthy levels in the western part of the county and air quality in the eastern end dropped from good to moderate.

Health department spokesman Tim O'Connor said this afternoon that people with lung ailments, children and the elderly should avoid spending time outside. Everyone else should not engage in strenuous exercise outdoors.

No local or regional departments reported any fires overnight in Palm Beach County that would blanket the southern reaches.

"I had discounted that (fire in the lake bed) because we hadn't gotten any calls from Palm Beach County other than in Boca," said Bill Berry, duty officer supervisor for the state's Division of Forestry in the county.

The Lake Okeechobee fire is causing a smoky haze throughout the Treasure Coast. And because of its size and the shifting wind direction, it is quite possibly this county's smoke source too, Berry said.

The fire grew overnight when the wind shifted and two wildfires merged. Monday morning Florida's Division of Forestry in the Treasure Coast reported the fires are 5 miles long and contained to the dry marsh and grass islands in the lake.

Boca Raton fire dispatchers thought there was possibly a controlled burn by Palm Beach County Fire Rescue west of Delray Beach.

Palm Beach County Fire Rescue Chief Steve Delai heard it may have been a controlled burn in the Everglades Agriculture area. Division of Forestry?

Nope. Division of Forestry didn't know of one, Berry said. If there were a burn out there overnight, that's news to them and illegal to boot.

But Berry did have word from Broward County of a condominium fire. Broward County Fire Rescue Dispatch reports that a commercial fire in Lauderhill began at 1:24 a.m.

"That's not us," says Lauderhill Fire Rescue spokesman Lt. Jeff Levy. "We did have a fire at 1:30 in the morning. But our fire's been out for a couple hours," he said.

"I did hear a report down here that something was burning in the Everglades."